This is a continuation of pending international application PCT/EP98/03065 filed on May 25, 1998.
1. Field of the Invention
The present invention relates to a medical instrument that is disassemblable into several components, in particular into a handle and a tubular shaft, one component, in particular the tubular shaft, being rotatable with respect to a further component, in particular the handle, by means of a rotary element arranged on the further component; having a coupling for detachable rotationally engaged connection of the one component to the rotary element of the further component, the coupling having two coupling halves which engage into one another along a coupling axis.
2. Related Prior Art
A medical instrument of this kind is marketed by the company styled Karl Storz GmbH and Co.
Medical instruments that are disassemblable into several components are widely used in surgery. Instruments suitable for minimally invasive surgery are configured as tubular shaft instruments which have a proximal handle and a tubular shaft. A working insert, which has at its distal end, for example, spatulas, needles, electrodes, loops, mouth parts functioning as scissors or forceps, and the like, is guided through the tubular shaft.
Disassembly of the instruments into handle, tubular shaft, and working insert allows optimum cleaning, as well as flexible utilization of the instrument by combining different components with one another.
Connection of the components must, however, proceed easily and quickly, so as to allow components to be exchanged, possibly even during the operation, without disrupting the proper execution of the operation.
One difficulty in connecting the components, usually a handle to a tubular shaft containing the working insert, arises from the fact that it is desirable for the tubular shaft to be connected rotatably about its longitudinal axis to the handle. The reason is that mouth parts can then be brought into any desired rotational position with respect to the handle, so that the surgeon can establish the most favorable relative rotational position between handle and mouth parts.
One known detachable rotationally engaged connection between handle and tubular shafts is accomplished by a coupling in which a polygonal member is provided.
In instruments of the Storz company, the coupling comprises an externally hexagonal member which engages in tight-fitting and positive and thus rotationally engaged fashion into an internally hexagonal member of female configuration on the coupling half of the handle. The female half of the coupling is connected to a rotary element so that the tubular shaft can rotate relative to the handle via the rotary element.
When connecting the two coupling halves, however, the problem arises that introduction of the polygonal member into the female shape by simple sliding or insertion into one another is not possible in every rotational position of the coupling halves, but rather is possible only if the externally hexagonal member is exactly in alignment with the internally hexagonal member. If such is not the case, the coupling halves must be rotated until they are exactly in alignment. This is cumbersome, complicates the process of closing the coupling, and requires close attention.
It is therefore the object of the invention to create a medical instrument that is disassemblable into several components, in which connection of the components can be performed quickly and easily and without close attention.
According to the present invention, the object is achieved, in an instrument of the kind cited initially, in that there is arranged on each coupling half, at a radial spacing from the coupling axis, at least one tooth adjacent to which in the circumferential direction is at least one gap into which a tooth of the other coupling half can enter and fit; and that each tooth is equipped in the circumferential direction with a bevel.
This yields a self-orienting coupling in which the two coupling halves are constrainedly guided by the beveled teeth while being connected. The need for a rotary motion to be performed consciously by the person fitting the two components together, in order to fit the two coupling halves into one another, is thus eliminated.
The reason is that because teeth with a bevel are provided, the coupling halves are deflected, as they are axially fitted together and encounter one another, regardless of their position, in such a way that the teeth slide past one another and are involuntarily introduced into adjacent gaps. The person fitting together the components therefore does not need to ensure that the coupling halves are correctly oriented; this is a decisive advantage, especially when components are being exchanged during an operation. The process of fitting together the coupling halves and thus the components proceeds particularly quickly, and requires neither concentration nor attention on the part of the person fitting the components together.
In an embodiment of the invention, each tooth is equipped with a bevel on either side of a tip.
The advantage of this feature is that the teeth are deflected in one or the opposite circumferential direction depending on how they encounter one another, and the teeth can enter into the gaps in aligned fashion after a relatively short rotational movement. In the case of teeth having only one bevel, deflection always occurs only in one circumferential direction.
In a further embodiment, two teeth are provided on each coupling half.
This feature has the advantage of ensuring secure meshing of the coupling halves with a relatively small rotation angle.
In a particularly preferred embodiment, two teeth are provided on one coupling half, and four teeth on the second coupling half.
This has the advantage of ensuring that two teeth encounter each other in every case, thus making possible secure meshing. The stress on the four teeth is minimized, so that the four teeth wear away less quickly and the service life of the coupling is increased. This makes it possible to arrange the four teeth on the instrument half which is more valuable or which is intended to have a longer service life.
In a further embodiment, the bevels of the teeth are at an acute angle to one another.
This embodiment offers the advantage of ensuring, because of the relatively sharply inclined contact surfaces, that the coupling halves are guided securely into one another with a relatively long axial coupling travel and a relatively small relative rotation of the coupling halves.
In the case of a tooth with only one bevel, the tip is located approximately on the extension of one tooth flank, and thus constitutes the acute angle.
In a further embodiment, the bevels of the teeth are at an oblique angle to one another.
This feature allows teeth with a low overall height.
In a particularly preferred embodiment, the bevels of the teeth are at an angle of approximately 90 degrees to one another.
This geometry offers the advantage of a low overall height while at the same time allowing the coupling halves to be guided securely into one another.
In a further preferred embodiment, the tips of the teeth have sharp edges.
The advantage here is to ensure, even if two tips encounter one another diametrically, that they slide immediately in one direction or another, and thus that the teeth are introduced into the corresponding gaps.
In a further embodiment, the tips of the teeth are rounded.
The advantage of this feature is that the teeth are more resistant to wear phenomena when the tips encounter one another directly.
In a further embodiment of the invention, the bevels of the teeth are curved outward in profile.
The advantage of this feature is that two teeth which encounter one another at their bevels as the coupling halves are being inserted into one another are essentially in only point contact during the rotational movement caused as the teeth encounter each other, and the rotation operation therefore proceeds with very little friction.
In a further embodiment of the invention, the teeth have magnetic tips, the magnetic tips of the one coupling half being opposite in polarity to the magnetic tips of the other coupling half.
The feature has the advantage that if the tips happen to be exactly aligned with one another, the opposite polarities of the tips ensure that because of the repulsive forces, they are deflected in one direction or the other even before meeting, so that the self-orienting or self-aligning operation proceeds particularly reliably and gently, thus helping to reduce material wear especially in the case of very slender instruments.
In a further embodiment, the teeth of one coupling half are joined to one another circumferentially via material bridges, and the material bridges have radially set-back recesses into which the teeth of the other coupling half engage in such a way that the two coupling halves are inhibited in terms of axial separation.
The advantageous aspect of this feature is that the two closed coupling halves can slide apart axially only after overcoming a resistance.
In a preferred embodiment, the two components are locked in terms of axial separation by an interlock that is separate from the coupling.
The advantage here is that the interlock can be arranged anywhere within the region in which the two components engage into one another. This moreover makes possible a particularly simple configuration, for example in the form of a snap groove on one component and a snap lug on the other component.
In a further embodiment of the invention, in a tubular shaft instrument four teeth are configured on the exterior of the tubular shaft, and at an axial spacing therefrom an annular groove of the interlock is cut in; and two diametrically opposite teeth are provided on the inner side of the rotary element on the handle, a locking element which engages inhibitingly into the annular groove being provided on the handle.
The four teeth on the exterior of the tubular shaft are provided at points which are favorably located for machining; the teeth can be machined out from a solid material. It is equally simple to recess the annular groove into the exterior of the tubular shaft.
All that is necessary is to cut out the two diametrically opposite teeth from the inner side of the rotary element. The locking element which engages into the annular groove in order to bring about axial inhibition can be provided on the handle in a user-friendly arrangement. This is easy in terms of production engineering, and easy to manipulate.
It is understood that the features mentioned above and those yet to be explained below can be used not only in the respective combinations indicated, but also in other combinations or in isolation, without leaving the context of the present invention.